Rapid tunneling method in gas-containing coal seams based on hydraulic fracturing pressure relief

Abstract

The present invention belongs to the field of rock burst and gas prevention and control in coal mines, and specifically relates to a method for rapid tunneling in gas-bearing coal seams based on hydraulic fracturing and pressure relief, comprising constructing a directional main borehole in a transport chute and a return air chute from a main transport tunnel, constructing a directional branch borehole from the directional main borehole into the first working face mining area; hydraulic fracturing and pressure relief of the coal seam using the directional branch borehole and the directional main borehole; tunneling the transport chute from the main transport tunnel, then tunneling a cut hole from the transport chute toward the return air chute, and finally tunneling the return air chute from the cut hole toward the return air tunnel; during tunneling, air is allowed to flow in through the transport chute and out through the return air chute; tunneling is performed on the next working face in the above manner. The present invention relieves pressure in the chute through the directional main borehole and relieves pressure in the working face mining area through the directional branch borehole, thereby forming a smooth path for gas extraction. It can also extract newly generated gas from the tunneling face, thereby preventing rock burst and gas from affecting tunneling.

Description

Technical Field

[0001] The present invention belongs to the field of coal mine rock burst and gas prevention and control, and particularly relates to a method for rapid tunneling in a gas-containing coal seam based on hydraulic fracturing and pressure relief. Background Art

[0002] Longwall caving is the most common method used in coal production. To prevent gas disasters caused by gas accumulation in the goaf, retreating coal seams is required. This requires pre-excavating haul chutes, return air chutes, and cut holes to and from the working face. However, tunneling is generally one-way, from one end of the tunnel to the other. This prevents a smooth ventilation path from forming at the face, resulting in high levels of coal dust. In gas-bearing coal seams with a tendency to impact, poor ventilation can easily lead to gas accumulation, causing gas poisoning and, in severe cases, gas explosions. Furthermore, rockbursts can occur during tunneling due to the coal seam's tendency to impact. Therefore, minimizing the impact of gas and rockbursts on tunneling, improving ventilation quality, and ensuring tunneling efficiency are key to improving coal production efficiency. Summary of the Invention

[0003] In view of the above-mentioned deficiencies of the prior art, the present invention proposes a method for rapid tunneling in a gas-containing coal seam based on hydraulic fracturing and pressure relief, which comprises the following steps:

[0004] S1: Construct a directional main borehole in the transport chute along the axial direction of the transport chute from the main transport tunnel, and construct a directional main borehole in the return air chute along the axial direction of the return air chute from the main return air tunnel; construct several directional branch boreholes from the directional main borehole to the first working face mining area; hydraulic fracturing and pressure relief are carried out on the coal seams in the first working face mining area using the directional branch boreholes, and the fractures formed by hydraulic fracturing are connected; hydraulic fracturing and pressure relief are carried out on the coal seams in the transport chute and return air chute using the directional main borehole;

[0005] S2: Excavate the transport chute from the transport tunnel, then excavate a cut-eye from the transport chute toward the return air chute, and finally excavate the return air chute from the cut-eye toward the return air tunnel; during the excavation process, air flows in through the transport chute and flows out through the return air chute;

[0006] S3: Excavate the next working face according to steps S1-S2.

[0007] Preferably, in step S1, the directional branch holes constructed from the transport chute and the return air chute intersect in the mining area of ​​the first working face.

[0008] Preferably, in step S2, before excavation, air is allowed to flow in through the transport chute and out through the return air chute to pre-extract gas from the first working face.

[0009] Preferably, in step S3, the next working face is a second working face adjacent to the first working face, a section coal pillar is left between the second working face and the first working face, and the second working face is rapidly excavated in the tunnel according to steps S1-S2; then, a section coal pillar is continued to be left between the second working face and the previous working face, and the next working face is rapidly excavated in the tunnel according to steps S1-S2.

[0010] Preferably, in step S3, the next working surface is an Nth working surface that is spaced apart from the first working surface by several working surfaces.

[0011] Preferably, in step S3, the gas content of the separated working surfaces is lower than that of the first working surface and the Nth working surface.

[0012] Preferably, for the plurality of spaced working surfaces, the method further comprises:

[0013] S4: Construct hydraulic fracturing drill holes in the cut-eye tunnel from the Nth working face cut-eye toward the first working face cut-eye direction, and decompress the coal seam in the cut-eye tunnel through hydraulic fracturing; then, excavate the cut-eye tunnel in the same direction;

[0014] S5: From the main transport tunnel, hydraulic fracturing holes are constructed along the axial direction of the transport chute of several separated working faces. From the main transport tunnel, hydraulic fracturing holes are constructed along the axial direction of the return air chute of several separated working faces. The coal seams in the return air chute and transport chute of several separated working faces are depressurized by hydraulic fracturing. Then, excavation of the return air chute and transport chute of several separated working faces is started from the main transport tunnel.

[0015] Preferably, in step S4, the first working face transport chute and the Nth working face return air chute are sealed so that the air flows from the Nth working face transport chute and the cut eye, through the cut eye connecting lane, to the first working face cut eye and return air chute.

[0016] Preferably, in step S5, the transport chute of the Nth working face is sealed so that the air flows from the return air chute and transport chute of several separated working faces, through the cut-eye connecting lanes, to the cut-eye and return air chute of the first working face.

[0017] Preferably, it also includes S6: constructing a sealing wall in the cut-eye connecting tunnel to form a cut-eye with several separated working faces, disconnecting the return air chute of the several separated working faces from the transport tunnel, and excavating in the reverse direction to connect it with the return air tunnel.

[0018] Preferably, the transport main tunnel is for transporting uphill, and the corresponding return air main tunnel is for returning air uphill.

[0019] The beneficial technical effects of the present invention are: 1. The tunnel excavation method of the present invention utilizes directional main drilling holes to hydraulically fracture and depressurize the coal seams in the transport chute and the return air chute, and utilizes directional branch holes to hydraulically fracture and depressurize the coal seams in the working face mining area. A smooth flow path for gas is formed based on the directional drilling holes and their fracturing cracks, and the newly generated gas at the tunnel excavation face can also be quickly extracted to avoid the impact of impact ground pressure and gas on tunnel excavation. The present invention can depressurize and extract gas from the entire working face during the excavation process.

[0020] 2. The present invention can quickly complete the rapid excavation work of the working face with relatively low gas concentration by setting the cut-eye connecting tunnel. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic plan view of the rapid excavation of the first working face tunnel of the present invention;

[0022] Figure 2 This is a schematic plan view of the rapid excavation of the second working face tunnel in the first embodiment of the present invention;

[0023] Figure 3 This is a schematic plan view of the rapid excavation of the fourth working face tunnel and the cut-eye connecting tunnel in the second embodiment of the present invention;

[0024] Figure 4 This is a schematic plan view of the rapid excavation of the second and third working faces of the tunnel according to the second embodiment of the present invention;

[0025] Figure 5 This is a schematic plan view of each working face after all working face tunnels are rapidly excavated in the second embodiment of the present invention;

[0026] In the figure: the arrow indicates the direction of tunnel excavation; return air tunnel 1, transport tunnel 2, return air chute 3, transport chute 4, cut eye 5, directional main drill hole 6a, directional branch hole 6b, cut eye connecting tunnel 7, first sealing wall 8, second sealing wall 9, hydraulic fracturing drill hole 10, and section coal pillar 11. DETAILED DESCRIPTION

[0027] The specific embodiments of the present invention are described below with reference to the accompanying drawings.

[0028] Example 1

[0029] like Figure 1-Figure 2 As shown, the present invention proposes a method for rapid tunneling in a gas-containing coal seam based on hydraulic fracturing and pressure relief, comprising the following steps:

[0030] S1: If Figure 1As shown, a directional main drill hole 6a is constructed from the transport tunnel 2 along the axial center of the transport chute 4, and a directional main drill hole 6a is constructed from the return air tunnel 1 along the axial center of the return air chute 3. The transport chute 4 and the return air chute 3 are perpendicular to the transport tunnel 2 and the return air tunnel 1. The length direction of the directional main drill hole 6a is consistent with the length direction of the transport chute 4 and the return air chute 3. The directional main drill hole 6a is a drill hole with a larger aperture.

[0031] A plurality of directional branch holes 6b are constructed from the directional main borehole 6a toward the first working face mining area (referring to the portion mined by the longwall caving method using a coal mining machine) and the cut-hole 5. The plurality of directional branch holes 6b are spaced apart along the length direction of the directional main borehole 6a, including directional branch holes 6b constructed from the transport chute 4 toward the return air chute 3, and directional branch holes 6b constructed from the return air chute 3 toward the transport chute 4. The directional branch holes 6b constructed from the transport chute 4 and the return air chute 3 intersect within the first working face. The directional branch holes 6b are used to hydraulically fracture and decompress the coal seams in the first working face mining area and the cut-hole 5. The fractures formed by the hydraulic fractures are connected. The directional main borehole 6a is used to hydraulically fracture and decompress the coal seams at the transport chute 4 and the return air chute 3. Preferably, after the hydraulic fracturing, proppant is injected into the fractures to support the fractures.

[0032] S2: If Figure 1 As shown, air from the transport tunnel 2 flows through the directional main drill hole 6a and its hydraulic fractures in the transport chute 4 into the directional branch hole 6b and its hydraulic fractures in the first working face mining area, carrying gas in the coal seam and then flowing out through the directional main drill hole 6a and its hydraulic fractures in the return air chute 3 to the return air tunnel 1. This gas extraction method facilitates the air to enter the coal seam of the first working face and forms a smooth ventilation path, which is beneficial for gas extraction.

[0033] Under this highly efficient gas extraction, the above ventilation path remains unchanged and tunnel excavation work is carried out on the first working face:

[0034] Tunnel excavation is carried out from the transport tunnel 2 to the transport chute 4. Prior to excavation, the coal seam at the transport chute 4 has been depressurized by hydraulic fracturing using the directional main borehole 6a, and gas pre-extraction has been carried out, which can provide a relatively safe environment for the excavation of the transport chute 4. During the excavation of the transport chute 4, the newly generated gas at the tunnel face will flow from the transport chute 4 into the directional branch holes 6b and their hydraulic fractures in the first working face mining area, and then carry the gas in the first working face mining area and flow out through the directional main borehole 6a and its hydraulic fractures in the return air chute 3 to the return air tunnel 1.

[0035] After the transport chute 4 is excavated, a cut hole 5 is excavated from the transport chute 4 toward the return air chute 3. At this time, part of the air entering the transport chute 4 flows into the first working face mining area through the directional branch holes 6b and their hydraulic fractures, carrying gas from the first working face mining area and then entering the directional main drill hole 6a and its hydraulic fractures in the return air chute 3. Part of the air carrying the newly generated gas from the tunnel face passes through the directional branch holes 6b and their hydraulic fractures in the cut hole 5 and then enters the directional main drill hole 6a and its hydraulic fractures in the return air chute 3, and finally flows out to the return air main tunnel 1.

[0036] After the cut-eye 5 is excavated, the return air chute 3 is excavated from the cut-eye 5 toward the return air tunnel 1. Before excavation, the coal seam at the return air chute 3 has been depressurized by hydraulic fracturing using the directional main borehole 6a, and gas pre-extraction has been carried out, which can provide a relatively safe environment for the excavation of the return air chute 3. At this time, part of the wind entering the transport chute 4 will flow into the first working face mining area from the directional branch hole 6b and its fracturing cracks, and after carrying gas from the first working face mining area, enter the directional main borehole 6a and its fracturing cracks in the return air chute 3. Part of the wind will enter the return air chute 3 through the cut-eye 5, carry the newly generated gas excavated at the face of the return air chute 3, and then enter the directional main borehole 6a and its fracturing cracks in the unexcavated return air chute 3, and finally flow out to the return air tunnel 1.

[0037] S3: If Figure 2 As shown, a section coal pillar 11 is left between the first working face, and the second working face is rapidly excavated according to steps S1-S2. Then, a section coal pillar 11 is left between the previous working face, and the next working face is rapidly excavated according to steps S1-S2.

[0038] Example 2

[0039] like Figure 1 、 Figure 3-Figure 5 As shown, the present invention proposes a method for rapid excavation of a gas-containing coal seam tunnel, comprising the following steps:

[0040] S1: If Figure 1 As shown, a directional main drill hole 6a is constructed from the transport tunnel 2 along the axial center of the transport chute 4, and a directional main drill hole 6a is constructed from the return air tunnel 1 along the axial center of the return air chute 3. The transport chute 4 and the return air chute 3 are perpendicular to the transport tunnel 2 and the return air tunnel 1. The length direction of the directional main drill hole 6a is consistent with the length direction of the transport chute 4 and the return air chute 3. The directional main drill hole 6a is a drill hole with a larger aperture.

[0041] A plurality of directional branch holes 6b are constructed from the directional main borehole 6a toward the first working face mining area (referring to the portion mined by the longwall caving method using a coal mining machine) and the cut-hole 5. The plurality of directional branch holes 6b are spaced apart along the length direction of the directional main borehole 6a, including directional branch holes 6b constructed from the transport chute 4 toward the return air chute 3, and directional branch holes 6b constructed from the return air chute 3 toward the transport chute 4. The directional branch holes 6b constructed from the transport chute 4 and the return air chute 3 intersect within the first working face. The directional branch holes 6b are used to hydraulically fracture and decompress the coal seams in the first working face mining area and the cut-hole 5. The fractures formed by the hydraulic fractures are connected. The directional main borehole 6a is used to hydraulically fracture and decompress the coal seams at the transport chute 4 and the return air chute 3. Preferably, after the hydraulic fracturing, proppant is injected into the fractures to support the fractures.

[0042] S2: If Figure 1 As shown, air from the transport tunnel 2 flows through the directional main drill hole 6a and its hydraulic fractures in the transport chute 4 into the directional branch hole 6b and its hydraulic fractures in the first working face mining area, carrying gas in the coal seam and then flowing out through the directional main drill hole 6a and its hydraulic fractures in the return air chute 3 to the return air tunnel 1. This gas extraction method facilitates the air to enter the coal seam of the first working face and forms a smooth ventilation path, which is beneficial for gas extraction.

[0043] Under this highly efficient gas extraction, the above ventilation path remains unchanged and tunnel excavation work is carried out on the first working face:

[0044] Tunnel excavation is carried out from the transport tunnel 2 to the transport chute 4. Prior to excavation, the coal seam at the transport chute 4 has been depressurized by hydraulic fracturing using the directional main borehole 6a, and gas pre-extraction has been carried out, which can provide a relatively safe environment for the excavation of the transport chute 4. During the excavation of the transport chute 4, the newly generated gas at the tunnel face will flow from the transport chute 4 into the directional branch holes 6b and their hydraulic fractures in the first working face mining area, and then carry the gas in the first working face mining area and flow out through the directional main borehole 6a and its hydraulic fractures in the return air chute 3 to the return air tunnel 1.

[0045] After the transport chute 4 is excavated, a cut hole 5 is excavated from the transport chute 4 toward the return air chute 3. At this time, part of the air entering the transport chute 4 flows into the first working face mining area through the directional branch holes 6b and their hydraulic fractures, carrying gas from the first working face mining area and then entering the directional main drill hole 6a and its hydraulic fractures in the return air chute 3. Part of the air carrying the newly generated gas from the tunnel face passes through the directional branch holes 6b and their hydraulic fractures in the cut hole 5 and then enters the directional main drill hole 6a and its hydraulic fractures in the return air chute 3, and finally flows out to the return air main tunnel 1.

[0046] After the cut-eye 5 is excavated, the return air chute 3 is excavated from the cut-eye 5 toward the return air tunnel 1. Before excavation, the coal seam at the return air chute 3 has been depressurized by hydraulic fracturing using the directional main borehole 6a, and gas pre-extraction has been carried out, which can provide a relatively safe environment for the excavation of the return air chute 3. At this time, part of the wind entering the transport chute 4 will flow into the first working face mining area from the directional branch hole 6b and its fracturing cracks, and after carrying gas from the first working face mining area, enter the directional main borehole 6a and its fracturing cracks in the return air chute 3. Part of the wind will enter the return air chute 3 through the cut-eye 5, carry the newly generated gas excavated at the face of the return air chute 3, and then enter the directional main borehole 6a and its fracturing cracks in the unexcavated return air chute 3, and finally flow out to the return air tunnel 1.

[0047] S3: If Figure 3 As shown, the fourth working face is rapidly excavated according to steps S1-S2, and there are a second working face and a third working face between the first working face and the fourth working face. The preferred application of the second embodiment is that the coal seam gas content of the second working face and the third working face is low, and the coal seam gas content of the first working face and the fourth working face is high.

[0048] S4: As Figure 3 As shown, a hydraulic fracturing borehole 10 is constructed from the fourth working face cut 5 to the first working face cut 5 to hydraulically fracture and decompress the coal seam in the cut-eye tunnel 7; the hydraulic fracturing borehole 10 is a borehole with a larger aperture; preferably, after hydraulic fracturing, a proppant is injected into the fracture to support the fracture;

[0049] The first sealing wall 8 is used to seal the transport chute 4 of the first working face and the return air chute 3 of the fourth working face, so that the air flows from the transport chute 4 and the cut-hole 5 of the fourth working face, through the hydraulic fracturing borehole 10 and its fracturing fissures in the cut-hole connecting lane 7, to the cut-hole 5 and the return air chute 3 of the first working face;

[0050] Keeping the above ventilation path unchanged, the cut-eye tunnel 7 is excavated from the fourth working face cut-eye 5 toward the first working face cut-eye 5. Before excavation, the coal seam in the cut-eye tunnel 7 has been depressurized using the hydraulic fracturing borehole 10, and gas pre-extraction has been carried out, which can provide a relatively safe environment for the excavation of the cut-eye tunnel 7. During the excavation of the cut-eye tunnel 7, the newly generated gas at the tunnel face will also flow from the hydraulic fracturing borehole 10 and its fracturing fissures in the unexcavated cut-eye tunnel 7 into the first working face cut-eye 5 and the return air chute 3, and then out to the return air tunnel 1.

[0051] S5: If Figure 4As shown, a hydraulic fracturing borehole 10 is constructed along the axial center of the return air chute 3 and the transport chute 4 of the second working face and the third working face from the main transport tunnel 2; hydraulic fracturing and pressure relief are performed on the coal seams in the return air chute 3 and the transport chute 4 of the second working face and the third working face through the hydraulic fracturing borehole 10; the hydraulic fracturing borehole 10 is a borehole with a larger aperture; preferably, proppant is injected into the fracturing fissure after hydraulic fracturing to support the fracturing fissure;

[0052] The first sealing wall 8 is used to seal the transport chute 4 of the fourth working face, so that the air flows from the hydraulically fractured boreholes 10 and their fractured fissures in the transport chute 4 of the second and third working faces, and the hydraulically fractured boreholes 10 and their fractured fissures in the return air chute 3, into the cut-hole tunnel 7, and then through the cut-hole 5 of the first working face and the return air chute 3, out to the return air tunnel 1;

[0053] Keeping the above ventilation path unchanged, the transport chute 4 and the return air chute 3 of the second and third working faces are excavated from the transport tunnel 2 toward the cut-eye tunnel 7. Before excavation, the coal seams in the transport chute 4 and the return air chute 3 of the second and third working faces have been depressurized by hydraulic fracturing, and gas pre-extraction has been carried out, which can provide a relatively safe environment for the excavation of the transport chute 4 and the return air chute 3 of the second and third working faces. During the excavation of the transport chute 4 and the return air chute 3 of the second and third working faces, the newly generated gas at the tunnel face will flow into the cut-eye tunnel 7 from the hydraulic fracturing boreholes 10 and their fracturing fissures in the transport chute 4 of the unexcavated second and third working faces, and from the hydraulic fracturing boreholes 10 and their fracturing fissures in the return air chute 3, and then flow out to the return air tunnel 1 through the cut-eye 5 and the return air chute 3 of the first working face.

[0054] S6: As Figure 5 As shown, at the positions of the coal pillars 11 between the first working face and the second working face, between the second working face and the third working face, and between the third working face and the third working face, a second sealing wall 9 is constructed in the cut-hole tunnel 7 to form the second working face cut-hole 5 and the third working face cut-hole 5;

[0055] Disconnect the return air chute 3 of the second working face and the third working face from the transport tunnel 2, and reversely excavate the return air chute 3 of the second working face and the third working face to connect them with the return air tunnel 1.

[0056] Afterwards, the first sealing wall 8 is used to close the transport chute 4 and return air chute 3 of the second working face, the third working face and the fourth working face, and the connection between the transport chute 4 and the transport main tunnel 2, and the return air chute 3 and the return air main tunnel 1 of the second working face, the third working face and the fourth working face is disconnected respectively, and the first working face is ready for mining.

[0057] The transport tunnel 2 in the first and second embodiments can also be used for uphill transport, and the corresponding return air tunnel 1 can be used for uphill return air. The coal dust generated by tunneling at the tunnel face and the newly generated gas at the tunnel face have the same flow direction, and some of the coal dust will remain in the directional main borehole 6a, directional branch boreholes 6b, hydraulic fracturing boreholes 10, and fracturing fissures. This can reduce coal dust at the tunnel face and optimize the working environment for workers.

[0058] The present invention is not limited to the above-mentioned optimal implementation mode. Anyone can derive other various forms of methods under the inspiration of the present invention. However, any technical solution that is the same or similar to that of the present application falls within the scope of protection of the present invention.

Claims

1. A method for rapid tunneling in gas-bearing coal seams based on hydraulic fracturing and pressure relief, characterized in that: The steps include: S1: Construct a directional main borehole in the transport chute along the axial direction of the transport chute from the main transport tunnel, and construct a directional main borehole in the return air chute along the axial direction of the return air chute from the main return air tunnel; construct several directional branch boreholes from the directional main borehole to the first working face mining area; hydraulic fracturing and pressure relief are carried out on the coal seams in the first working face mining area using the directional branch boreholes, and the fractures formed by hydraulic fracturing are connected; hydraulic fracturing and pressure relief are carried out on the coal seams in the transport chute and return air chute using the directional main borehole; S2: Excavate the transport chute from the transport tunnel, then excavate a cut-eye from the transport chute toward the return air chute, and finally excavate the return air chute from the cut-eye toward the return air tunnel; during the excavation process, air flows in through the transport chute and flows out through the return air chute; S3: tunneling the next working face according to steps S1-S2; the next working face is the next working face that is spaced several working faces from the first working face. N working face; S4: From N From the working face cut-eye, hydraulic fracturing drilling is carried out in the cut-eye tunnel in the direction of the first working face cut-eye, so as to relieve the pressure of the coal seam in the cut-eye tunnel by hydraulic fracturing; then the cut-eye tunnel is excavated in the same direction; S5: From the main transport tunnel, hydraulic fracturing holes are constructed along the axial direction of the transport chute of several separated working faces. From the main transport tunnel, hydraulic fracturing holes are constructed along the axial direction of the return air chute of several separated working faces. The coal seams in the return air chute and transport chute of several separated working faces are depressurized by hydraulic fracturing. Then, excavation of the return air chute and transport chute of several separated working faces is started from the main transport tunnel.

2. The method for rapid tunneling in a gas-containing coal seam based on hydraulic fracturing and pressure relief according to claim 1, characterized in that: In step S1, the directional branch holes constructed from the transport chute and the return air chute intersect in the mining area of ​​the first working face.

3. The method for rapid tunneling in a gas-containing coal seam based on hydraulic fracturing and pressure relief according to claim 1, characterized in that: In step S2, before excavation, air is allowed to flow in through the transport chute and out through the return air chute to pre-extract gas from the first working face.

4. The method for rapid tunneling in a gas-containing coal seam based on hydraulic fracturing and pressure relief according to claim 1, characterized in that: In step S4, the first working face transport chute and the second working face transport chute are sealed. N The working face return air chute makes the air flow direction from the first N The working face transport chute and cut eye pass through the cut eye connecting tunnel and reach the first working face cut eye and return air chute.

5. The method for rapid tunneling in a gas-containing coal seam based on hydraulic fracturing and pressure relief according to claim 4, characterized in that: In step S5, seal the N The working face transport chute makes the air flow direction from the return air chute and transport chute of several separated working faces, through the cutting eye connecting lane, to the first working face cutting eye and return air chute.

6. The method for rapid tunneling in a gas-containing coal seam based on hydraulic fracturing and pressure relief according to claim 5, characterized in that: It also includes S6: constructing a sealing wall in the cut-eye connecting tunnel to form a cut-eye of several separated working faces, disconnecting the return air chute of the several separated working faces from the transport tunnel, and excavating in the reverse direction to connect it with the return air tunnel.

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